Vehicle emergency communicators have been proposed for completing an emergency message operation. The emergency message operation involves transmitting an emergency message signal to a service center in the event of an emergency, e.g., detected by the deployment/inflation of an air bag. However, the air bag deployment signal may not be determined or transmitted when the ignition signal from the ignition switch is in an OFF-state. In other words, many vehicle emergency communicators of the prior art are constructed to determine and transmit the air bag deployment signal only when the ignition signal from the ignition switch is in an ON-state. However, when the ignition signal is out of order due to a broken wire, etc., the emergency communicator is unlikely to determine and transmit the air bag deployment signal, and the emergency message operation cannot be performed.
On the other hand, JP-A-2002-29364 describes a device with a plurality of transmission paths for the ignition signal. The technology described in JP-A-2002-29364 can be applied to an in-vehicle emergency communicator. As such, even if one of the transmission paths for the ignition signal fails, the emergency message operation can be appropriately performed using another transmission path. However, because the device includes a plurality of transmission paths for the ignition signal and also exclusive circuits thereto, the size of the device may be undesirably large, and/or the device may be more expensive.